1. Field of the Invention
The present invention relates to digital wireless communications systems of the type which employ portable, battery-powered communications devices, such as remote telemeters worn by ambulatory hospital patients for monitoring purposes. More particularly, the present invention relates to a network architecture, and an associated TDMA (time division multiple access) communications protocol, for facilitating the efficient and reliable exchange of information between portable wireless devices and centralized monitoring stations.
2. Description of the Related Art
Medical telemetry systems that allow the physiologic data of multiple, remotely-located patients to be monitored from a central location are known in the art. These systems typically comprise remote telemeters that remotely collect the physiologic data of respective patients and transmit the data over a wireless link to a centralized monitoring station. This physiologic data may include, for example, real-time electrocardiograph (ECG) waveforms, CO.sub.2 levels, and temperature readings. From the centralized monitoring station, a clinician can visually monitor the physiologic status, in real time, of many different patients. The central station may also run automated monitoring software for alerting the clinician whenever a predetermined physiologic event occurs, such as a cardiac arrythmia condition.
Remote telemeters of medical telemetry systems are generally of two types: instrument remote telemeters and ambulatory remote telemeters. An ambulatory remote telemeter is a portable, battery-powered device which permits the patient to be monitored while the patient is ambulatory. The ambulatory telemeter attaches to the patient by a strap or other attachment device, and receives the patient's physiologic data via ECG leads (and/or other types of sensor leads) which attach to the patient's body. The physiologic data is continuously transmitted to the central monitoring station by the telemeter's RF (radio frequency) transmitter to permit real-time monitoring. (A design of a remote transceiver which may be used in a two-way, ambulatory telemeter is described in the above-referenced provisional application.) Instrument remote telemeters operate in a similar manner, but receive the patient's physiologic data from a bedside monitor (or other instrument) over a hardwired link, such as an RS-232 connection. Instrument remote telemeters that transfer the physiologic data to the central station over a hardwired connection are also common.